package com.feng.dataStructures.linkedlist;

/**
 * @author fengsy
 * @date 6/13/21
 * @Description
 */
public class SinglyLinkedList {
    private Node head = null;

    public Node findByValue(int value) {
        Node p = head;
        while (p != null && p.data != value) {
            p = p.next;
        }
        return p;
    }

    public Node findByIndex(int index) {
        Node p = head;
        int position = 0;
        while (p != null && position != index) {
            position++;
            p = p.next;
        }
        return p;
    }

    public void insertToHead(int value) {
        Node newNode = new Node(value, null);
        insertToHead(newNode);
    }

    public void insertToHead(Node newNode) {
        if (head == null) {
            head = newNode;
        } else {
            newNode.next = head;
            head = newNode;
        }

    }

    public void insertTail(int value) {

        Node newNode = new Node(value, null);
        // 空链表，可以插入新节点作为head，也可以不操作
        if (head == null) {
            head = newNode;

        } else {
            Node q = head;
            while (q.next != null) {
                q = q.next;
            }
            newNode.next = q.next;
            q.next = newNode;
        }
    }

    public void insertAfter(Node p, int value) {
        Node newNode = new Node(value, null);
        insertAfter(p, newNode);
    }

    public void insertAfter(Node p, Node newNode) {
        if (p == null) {
            return;
        }

        newNode.next = p.next;
        p.next = newNode;
    }

    public void insertBefore(Node p, int value) {
        Node newNode = new Node(value, null);
        insertBefore(p, newNode);
    }

    public void insertBefore(Node p, Node newNode) {
        if (p == null) {
            return;
        }
        if (head == p) {
            insertToHead(newNode);
            return;
        }

        Node q = head;
        while (q != null && q.next != p) {
            q = q.next;
        }

        if (q == null) {
            return;
        }

        newNode.next = p;
        q.next = newNode;

    }

    public void deleteByNode(Node p) {
        if (p == null || head == null) {
            return;
        }

        if (p == head) {
            head = head.next;
            return;
        }

        Node q = head;
        while (q != null && q.next != p) {
            q = q.next;
        }

        if (q == null) {
            return;
        }

        q.next = q.next.next;
    }

    public void deleteByValue(int value) {
        if (head == null) {
            return;
        }

        Node p = head;
        Node q = null;
        while (p != null && p.data != value) {
            q = p;
            p = p.next;
        }

        if (p == null) {
            return;
        }

        if (q == null) {
            head = head.next;
        } else {
            q.next = q.next.next;
        }
        // 可重复删除指定value的代码
        /*
           if (head != null && head.data == value) {
           head = head.next;
           }
        
           Node pNode = head;
           while (pNode != null) {
           if (pNode.next.data == data) {
           pNode.next = pNode.next.next;
           continue;
           }
           pNode = pNode.next;
           }
         */
    }

    public void printAll() {
        Node p = head;
        while (p != null) {
            System.out.print(p.data + " ");
            p = p.next;
        }
        System.out.println();
    }

    // 判断true or false
    public boolean TFResult(Node left, Node right) {
        Node l = left;
        Node r = right;

        boolean flag = true;
        System.out.println("left_:" + l.data);
        System.out.println("right_:" + r.data);
        while (l != null && r != null) {
            if (l.data == r.data) {
                l = l.next;
                r = r.next;
                continue;
            } else {
                flag = false;
                break;
            }

        }

        System.out.println("什么结果");
        return flag;
        /* if (l==null && r==null){
           System.out.println("什么结果");
           return true;
        }else{
           return false;
        }*/
    }
    // 判断是否为回文

    public boolean palindrome() {
        if (head == null) {
            return false;
        } else {
            System.out.println("开始执行找到中间节点");
            Node p = head;
            Node q = head;
            if (p.next == null) {
                System.out.println("只有一个元素");
                return true;
            }
            while (q.next != null && q.next.next != null) {
                p = p.next;
                q = q.next.next;

            }

            System.out.println("中间节点" + p.data);
            System.out.println("开始执行奇数节点的回文判断");
            Node leftLink = null;
            Node rightLink = null;
            if (q.next == null) {
                // p 一定为整个链表的中点，且节点数目为奇数
                rightLink = p.next;
                leftLink = inverseLinkList(p).next;
                System.out.println("左边第一个节点" + leftLink.data);
                System.out.println("右边第一个节点" + rightLink.data);

            } else {
                // p q 均为中点
                rightLink = p.next;
                leftLink = inverseLinkList(p);
            }
            return TFResult(leftLink, rightLink);

        }
    }

    // 带结点的链表翻转
    public Node inverseLinkList_head(Node p) {
        // Head 为新建的一个头结点
        Node Head = new Node(9999, null);
        // p 为原来整个链表的头结点,现在Head指向 整个链表
        Head.next = p;
        /*
        带头结点的链表翻转等价于
        从第二个元素开始重新头插法建立链表
        */
        Node Cur = p.next;
        p.next = null;
        Node next = null;

        while (Cur != null) {
            next = Cur.next;
            Cur.next = Head.next;
            Head.next = Cur;
            System.out.println("first " + Head.data);

            Cur = next;
        }

        // 返回左半部分的中点之前的那个节点
        // 从此处开始同步像两边比较
        return Head;

    }

    // 无头结点的链表翻转
    public Node inverseLinkList(Node p) {

        Node pre = null;
        Node r = head;
        System.out.println("z---" + r.data);
        Node next = null;
        while (r != p) {
            next = r.next;

            r.next = pre;
            pre = r;
            r = next;
        }

        r.next = pre;
        // 返回左半部分的中点之前的那个节点
        // 从此处开始同步像两边比较
        return r;

    }

    public static class Node {
        private int data;
        private Node next;

        public Node(int data, Node next) {
            this.data = data;
            this.next = next;
        }

        public int getData() {
            return data;
        }
    }

    public static void main(String[] args) {

    }
}
